The US president told a conference in Philadelphia on Tuesday that he was working with European governments on a plan to “help reduce food prices”. An estimated 20 million tonnes of grain have been trapped in Ukraine – the world’s fifth-largest grain exporter – since the war began in late February, sparking fears of famine in some countries. When Russia invaded, it blocked the ports of the Black Sea of Ukraine. Russian and Ukrainian forces have also filled the surrounding waters with mines. Attempts to restart shipping failed and about 84 foreign ships were stranded in Ukrainian ports, many carrying grain. A huge diplomatic effort to rescue Ukraine’s grain has failed as it has always been transported by sea rather than by less reliable road or rail networks. In his speech, Biden said the grains could not “get out of the Black Sea because they will explode from the water”, referring to the floating mines. Instead, he said, Washington was working on a plan to export grain by rail, but noted that the Ukrainian railways were different from those of Europe – being slightly wider – so the grain would have to be transported on different trains across the border. “This is how we will build silos, temporary silos, on the border with Ukraine, including Poland,” Biden said. The grain could be transported from Ukrainian railway wagons to new silos and then to European freight wagons to “go out to ocean and cross the world,” he said, adding that the plan would take time. Subscribe to the First Edition, our free daily newsletter – every morning at 7 p.m. BST “This is just one of the many possible steps you can take to ensure food security. But we also need a green corridor for our ports, “Andriy Yermak, chief of staff to Ukrainian President Volodymyr Zelenskiy, said in an online post referring to the blockade. Ukraine’s agriculture ministry said on Tuesday that European countries were considering providing temporary silos to “preserve the crop and secure future grain supplies”. The halt in grain exports has contributed to what analysts have called a “perfect storm” on global food supplies, as farmers face rising costs for oil and fertilizers and the prolonged impact of labor restrictions by the coronavirus. The head of the African Union warned last month that the blockade of Ukrainian ports by Moscow was in danger of “a catastrophic scenario” of food shortages and rising prices. Reuters contributed to this report